Defective high-entropy rocksalt oxide with enhanced metal‒oxygen covalency for electrocatalytic oxygen evolution  

金属-氧共价性增强的缺陷态高熵岩盐型氧化物用于电催化析氧

作　　者：Fangming Liu Meng Yu Xiang Chen Jinhan Li Huanhuan Liu Fangyi Cheng 刘芳名;于勐;陈祥;李金翰;刘欢欢;程方益(南开大学化学学院,先进能源材料化学教育部重点实验室,新能源转化与存储交叉科学中心,天津300071)

机构地区：[1]Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education),Renewable Energy Conversion and Storage Center,College of Chemistry,Nankai University,Tianjin 300071,China

出　　处：《Chinese Journal of Catalysis》2022年第1期122-129,共8页催化学报（英文）

基　　金：国家重点研发计划纳米科技专项(2017YFA0206700);国家自然科学基金(21925503,21871149,51571125,51622102);111引智计划(B12015);中央高校基本科研业务费专项资金.

摘　　要：High‐entropy materials are emerging electrocatalysts by integrating five or more elements into one single crystallographic phase to optimize the electronic structures and geometric environments.Here,a rocksalt‐type high‐entropy oxide Mg_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2)Zn_(0.2)O(HEO)is developed as an electrocatalyst towards the oxygen evolution reaction(OER).The obtained HEO features abundant cation and oxygen vacancies originating from the lattice mismatch of neighboring metal ions,together with enlarged Co/Ni‒O covalency due to the introduction of less electronegative Mg and Zn.As a result,the HEO exhibits superior intrinsic OER activities,delivering a turnover frequency(TOF)15 and 84 folds that of CoO and NiO at 1.65 V,respectively.This study provides a mechanistic understanding of the enhanced OER on HEO and demonstrates the potential of high‐entropy strategy in developing efficient oxygen electrocatalysts by elaborately incorporating low‐cost elements with lower electronegativity.高熵材料可以在单一晶相中引入五种或五种以上元素以优化电子结构和配位环境,可作为一类新兴的电催化剂.本文制备了一种岩盐型高熵氧化物Mg_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2)Zn_(0.2)O(HEO)用于催化氧析出反应(OER).由于相邻的不同金属离子晶格失配,所制备的HEO具有丰富的缺陷.此外,电负性更小的Mg和Zn元素的存在使Co/Ni‒O共价性增强.得益于此,HEO在碱性条件下展现出优异的OER本征催化活性,其转换频率(TOF)在1.65 V时分别达到CoO和NiO的15和84倍.本文探究了HEO电催化性能提升机制,论证了通过合理添加低成本和低电负性元素的高熵策略在发展高效氧电催化剂方面的潜能.采用静电纺丝和热处理的方法制备了含有五种金属元素的HEO,X射线衍射(XRD)结果表明其为岩盐型晶体结构.X射线能量色散谱(EDS)和电感耦合等离子体发射光谱(ICP-OES)分析表明五种元素接近等摩尔比,且均匀分布.通过高分辨透射电子显微镜(HRTEM)发现HEO晶格中含有大量缺陷;同步辐射扩展X射线吸收精细结构(EXAFS)谱拟合数据显示HEO中Co和Ni的配位数相比CoO和NiO均有所降低,证实了缺陷的存在.此外,O 1s的X射线光电子能谱(XPS)和电子顺磁共振谱(EPR)进一步证明HEO含有大量氧缺陷.缺陷结构有利于配位不饱和的活性位点充分暴露,促进反应中间体的吸附,从而提升电催化活性.通过X射线吸收近边结构(XANES)谱分析了HEO中Co和Ni的电子结构信息.结果表明,相比CoO和NiO,HEO中Co和Ni的氧化态更低,因为HEO中电负性更低的Mg和Zn可以向O转移更多电子,使相邻的Co和Ni贡献更少电子.更高的电荷密度说明Co/Ni‒O键的共价性增强,与傅里叶变换的EXAFS谱中Co/Ni‒O键的键长变短相吻合.此外,Co和Ni2p的XPS结果表明,HEO表面Co(Ⅱ)和Ni(Ⅱ)成分占比较CoO和NiO更高,也证明HEO中Co/Ni‒O键具有更高的共价性.在1 M KOH中,HEO展现出优越的OER电催化性能,其达�

关 键 词：High-entropy material Rocksalt oxide Oxygen evolution reaction Electrocatalyst Defect Metal-oxygen covalency 

分 类 号：O643.36[理学—物理化学]